Remember when there were radicals? The whole scene -- with the tear gas, the billy clubs, the obscenities, the confrontations -- seems ancient by now, so much so it's become a regular subject for nostalgia. The same goes for the arts in general and dance in particular. Looking around at what's going down at the start of the 80's, it's hard to identify anything that seems to demand the label, "avant-garde," at least as it used to be understood in the '60's and early '70's. At dance events nowadays, there are no carloads of "fuzz" to stop the show or drag off the unruly. There's no scatology. There's nothing that could be remotely construed as politically inflammatory, and little that seems "outrageous" even from a purely esthetic standpoint.

Yet, though shock and violence have disappeared both as tactics and response, there remains a kind of dance that is conspicuously "offbeat" -- dance aimed at a different audience, and resting on a different scale of values than the work of such by now accepted practitioners of modern dance as, say, Paul Taylor, Alvin Ailey or even Merce Cunningham.

Perhaps one defining characteristics of such dance is that it hasn't made it to television, at least, until now. Hence "Beyond the Mainstream," which airs on Channel 26 Wednesday evening at 8 p.m., is something of a breakthrough. The hour-long survey of what's variously called avant-garde, or experimental, or "new," or post-Cunningham or post-Judson or post-modern dance, is a further installment in the PBS "Dance in America" series, which has finally taken the courageous step of examining the present-day "fringe" of the art and the developments that led to it.

The choreographers whose work is sampled in "Beyond the Mainstream" -- Trisha Brown, Laura Dean, Kei Takei, David Gordon, Steve Paxton and Yvonne Rainer -- are very different artists. A cynic might say that what they mostly have in common is being unknown to the general public, and attracting small audiences. But even superficially, there are artistic propensities they share that justify the group treatment. For one thing, they all eschew easy roads to popularity -- the gimmickry and trendiness that might assure them swifter or broader recognigtion. For another, they are each concerned in their separate ways with extending the perimeter of dance art by redefining its basic principles.

Historically -- and these six contemporary dance-makers are no exception -- the avent-garde has always been fueled by acts and postures of rebel-lion. Isadore Duncan was the most celebrated avant-gardiste of her day, and she was making war on the artificalities and decadent conventions of the classical ballet. It was in revot against Duncan's contemporary, Ruth St. Denis, that Martha Graham, Doris Humphrey, Charles Weidman and others of their generation set forth on their own heretical paths. The progeny of that generation also broke away, not so much in a spirit of artistic sedition as in assertion of personal autonomy, and they in turn -- Jose Limon, Anna Sokolow, Alvin Ailey, Alwin Nikolais, Erick Hawkins, Paul Taylor and Merce Cunningham being the chief figures -- formed the contributing rivulets of today's mainstream. Cunningham, however, became the link to the next upheaval -- along with Anna Halprin and James Waring, as well as composers John Cage and Robert Dunn, he fathered forth the next group of mavericks whose activities centered aroung Manhattan's Judson Church in the early '60's.

Of the "Beyond the Mainstream" choregraphers, all but Dean and Takei were associated with the Judson group. Some of the most exciting footage in the program is the black-and-white film material from that era, including a Claes Oldenburg (the involvement of plastic artists was one of the Judson hallmarks) "happening" in a park in 1965, with a man eating balloons and an American flag being dragged through a pool; a Rauschenberg event featuring nude women dancers and parachutes; and scenes from the nortorious Nine Evenings of Theatre and Engineering at the 69th Regiment Armory in 1966, with dancers, actors and musicans surrounded by the Frankenstein technology of the "multimedia" explosion. These pictures not only summon to instant life the charged iconociasm of those days, but also tend to underline how far from that atmosphere we've gravitated in little more than a decade.

Pretty much gone since the mid-'70's are anger, protest, nudity and sex. Today's fringe chororeography tends to be far more "laid back" and distanced than its counterparts a decade ago, for the most part. On the other hand, the main concerns and "parameters" (to use a favorite piece of '70's jargon) of the "Beyond the Mainstream" artists -- with a few exceptions -- go back to the Judson era, the chief differences being idiosyncratic to the individual choreographers involved.

Thus, there is the "factual" approach to dance movement -- part of the '60's de-sanctification of Art -- expounded by and exemplified in the works of Yonne Rainer (who's since given up dance for filmmaking) and carried over into the choreograhy of Trisha Brown, David Gordon and Steve Paxton. Dancers move through a work as if it were a piece of business being attended to, a task being executed, rather than some grand symbolic statement on the meaning of life. There's the interest in "process," the mechanics of getting things done, or the dynamics of growth.

There's also the sense of "non-linear" multichannel activity, which the age of TV itself has fostered. In one of Trisha Brown's pieces, she talks, while moving, about two different subjects, which she labels, "A" and "B," switching from one to the other and back abruptly, exactly as if she were rotating a selector dial. A certain kind of characteristically dry, deadpan wit also crops up -- David Gordon has a line of performers casually walking across the studio floor in jeans, sport clothes or suits to the music of the Entrance of the Shades from "Bayadere," in a poker-faced parody of this classic of "white" ballet. A sort of animal playfulness motivated other pieces, from Steve Paxton's "contact improvisation" rollings and sprawlings, to Trisha Brown's "Line-Up," its women in pajama-like togs transmitting a quirky shuffle walk form one to the next lke beads on a string.

Laura Dean, part of whose beguiling "Dance" is seen on the program, and Kei Taketi, represented by an excerpt from her monumental "Light," share something that was not part of the Jason canon -- a penchant for modular repetition, and a sense of ceremony, of ritual. Takei goes even further -- her mysterious, elemental dances enter the realm of metaphor. Alone among the six, she reestablishes the connection between dance and human universals that was a major preoccupation of earlier generations of choreographers. Unfortunately, the power of Takei's work seems more diminished by he scale and flatness of TV than other constituents of the program.

In general, however, "Beyond the Mainstream" upholds the general high standard of the "Dance in America" series, and it's put together in a fluid, freewheeling style that befits is subjects. What it needs most is amplification, and for this reason it ought to be supplemented on public TV by Michael Blackwood's excellent film "Making Dances," which touches some important bases -- Meredith Monk, Lucinda Childs and Douglas Dunn, for example -- in admirable depth.